Method of operating a vehicle transmission

ABSTRACT

Specific shift positions of an electrically actuated vehicle transmission, such as first to fifth, neutral and reverse gears, are detected by monitoring one or more characteristic electrical variables, e.g., actuator currents, during a shift movement of the transmission and by correlating increased or decreased levels of current with the arrival at or passage through the specific shift positions.

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application is a divisional of U.S. patentapplication Ser. No. 10/012,701, filed Dec. 7, 2001, which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] The invention relates to a method of detecting at least onepredetermined shift position of a vehicle transmission among a pluralityof different shift positions corresponding to different rotary transferratios between an input shaft and an output shaft. It further relates toa control device, to a vehicle transmission, as well as the use of themethod, the use of the control device, and the use of the vehicletransmission. In addition, the invention also relates to a method ofdetecting a position change in relation to a reference position of avehicle transmission.

[0003] A transmission in the present context means a device that can beshifted into different states, by an either stepwise or continuousvariation, to generate different rotary transfer ratios between twoshafts. The transmission is configured as a gear-changing transmissionor a cone-pulley transmission, or other appropriate mechanism. The shiftprocesses of the transmission can be controlled automatically ormanually, or in a partially automatic mode, or in an automated mode thatpermits manual intervention by the driver. A transmission in the senseof the present invention can be configured so that shifts from one gearratio to another cause an interruption in vehicle traction, or it can beconfigured to perform shifts without interrupting traction.

[0004] With preference, the transmission is configured as an automatictransmission which, in the context of the present invention, means atransmission that shifts without interrupting traction. With specialpreference, however, the transmission is configured as an automatedshift transmission, a term which is used in particular for atransmission in which the control of the shift process is automated butcauses an interruption in vehicle traction.

[0005] Transmissions as well as operating methods for transmissionsbelong to the known state of the art.

[0006] In a manual transmission, the gear shifts are performed manuallyby the driver. In principle, the driver is free to shift arbitrarilyfrom any gear into any other gear. The driver chooses when to shiftgears and which gear to shift into, based on certain criteria. Thedriver will decide to shift gears particularly in response to the soundof the engine and depending on which of the gears is currently engaged.

[0007] Errors in recognizing which gear is currently engaged, errors ofshifting into an other than the intended gear, judgment errors about theneed to shift gears, or other mistakes can cause damage to atransmission or can stall the engine of a vehicle. This kind ofsituation can occur, for example, in a vehicle coasting downhill withthe transmission set to the neutral position, if the driver's foot is onthe gas pedal so that the engine runs at a high rpm rate but the drivererroneously believes the transmission to be in first gear and thereforeshifts into second gear.

[0008] Also known are automated shift transmissions in which the shiftsare actuated by two electric motors. The electric motors apply a forceto a shifter finger. The shifter finger moves in a pattern that consistsof a selector track (also called neutral track) and shift tracksbranching off from the selector track. The first of the electric motorsmoves the shifter finger in the direction of the shift tracks whichterminate at the different gear positions, while the second of theelectric motors moves the shifter finger in the direction of theselector track where the transmission is in the neutral state.

[0009] The shifter finger position is monitored by displacement sensorswhich are arranged at the electric motors and work according to anincremental detection principle.

[0010] The shifter finger is controlled by the electric motors dependenton the position values generated by the incremental sensors.

[0011] Automated shift transmissions of the foregoing descriptionprovide a satisfactory level of shifting and driving comfort and aneconomical way of operating a vehicle.

[0012] However, there have been incidents where gear shifts whereperformed incorrectly by transmissions of this type. Incorrect gearshifts are detrimental to the driving comfort in a vehicle with anautomated shift transmission and will shorten the life of thetransmission.

OBJECT OF THE INVENTION

[0013] The present invention therefore has the objective of providing amethod of operating a vehicle transmission, as well as a transmissioncapable of performing the method, with an at least reduced incidence ofincorrect gear shifts, a longer operating life, and an improved level ofcomfort for the driver and passengers of a vehicle that is equipped withthe inventive transmission. In particular, the invention has theobjective of providing a method of operating a transmission, as well asa transmission capable of performing the method, wherein the currentshift position or shift movements from one position to another can bedetected and evaluated more accurately and reliably and whereindetection errors can be corrected, so that detected positions or shiftmovements reflect the actual positions or movements of the transmission.

SUMMARY OF THE INVENTION

[0014] To meet the objective stated above, the invention proposes amethod of detecting at least one predetermined gear-shift position of atransmission that has a plurality of different operating statescorresponding to different rotary transfer ratios between an input shaftand an output shaft of a vehicle transmission. A transmission that isoperable by the inventive method has a shift pattern with a selectortrack and shift tracks. A first shifter element, in particular a shifterfinger, is movable within the shift pattern. The transmission alsoincludes a second shifter element, in particular a shifter shaft or ashift rod. The transmission is further equipped with an actuator devicerunning under the control of an electrical control device to actuate atleast one of the first and second shifter elements. At least oneposition-sensor device is provided in the transmission to determine theposition of a movable element of the transmission.

[0015] The method according to the invention has the following steps:

[0016] a) When a set of predetermined conditions are present, anactuating force is applied by the actuator device to at least one of theshifter elements in accordance with a predetermined characteristic.

[0017] b) At least one characteristic electrical variable of theactuator device and/or the control device, particularly an electriccurrent, is monitored as a function of time.

[0018] c) The profile of the electrical variable as a function of timeis evaluated according to a predetermined evaluation characteristic todetermine a shift position that the transmission is set at. Thisdetermination is based on a functional dependency between the timeprofile of the characteristic electrical variable and the shiftposition.

[0019] The shift positions to be determined by the inventive methodinclude in particular at least one end position of a shift-track and/orat least one specific position in the selector track and/or any positionin the selector track.

[0020] The second shifter element, which consists of a shifter shaft, ashift rod, a shift fork, or a similar element, is connected to the firstshifter element.

[0021] The arrangement of a selector track and shift tracks, as well asthe first and second shifter elements, are part of a gear-shiftingmechanism.

[0022] At least one movable element of the gear-shifting mechanism, suchas the first or second shifter element, can be subjected to actuatingforces under the control of an actuator device, causing the element tomove, at least to the extent that the movement is not prevented by otherfactors or elements of the mechanism, such as end stops.

[0023] An actuator device in the sense of the present invention is adevice that can convert one form of energy into another, generating anoutput that actuates the shift mechanism or at least one of the movableelements of the shift mechanism. In particular, the actuator device hasat least one electric motor that converts electrical energy intomechanical motion. With preference, the actuator device has two electricmotors. The first motor, referred to as selector motor, can exert on thefirst shifter element a force in the direction of the selector track.The second motor, referred to as shifter motor, can exert on the firstshifter element a force in the direction of the shift tracks.

[0024] A shift track in the sense of the invention can mean a physicallyexisting shift track or a virtual shift track containing a position ofthe first shifter element where a predetermined gear or a predeterminedrotary transfer ratio of the transmission is engaged, or it can mean apair of shift tracks branching off from a given point of the selectortrack.

[0025] A virtual track means a concept where the shifter element canmove only along certain track-like paths, constrained by the nature ofcontrol signals generated by the actuator device or the control device.

[0026] The actuator device is controlled by a control device.

[0027] A control device in the sense of the invention means inparticular a device that supplies control signals and/or energy to theactuator device in accordance with a predetermined characteristic. Inparticular according to the inventive concept, the nature, duration,timing, direction, orientation, and force of the action exerted on theshift mechanism by the actuator device depends on the signals and/or onthe flow of energy transmitted from the control device to the actuatordevice.

[0028] The invention provides in particular that the control devicesupplies the actuator device with current, i.e., with electrical energy,according to a predetermined characteristic.

[0029] A control device in the sense of the invention can be designed toprovide energy and/or to control either the actuator device alone or atleast one other device in addition to the actuator device, for example aclutch. Under a preferred concept of the present invention, the controldevice controls the actuator device through one or more voltage signalswhich may be of a set magnitude or variable according to a predeterminedcharacteristic.

[0030] According to the invention, the transmission is equipped with aposition sensor device that serves to detect shift positions by sensingthe positions of components that are moved in the process of shifting.

[0031] A position sensor device in the present context means a device bywhich a position or a change of position can be detected in absolute orrelative terms. In particular, the position sensor device can consist ofa device that measures the length of a linear displacement or the angleof a rotary displacement. In particular, the position sensor device isconfigured to perform either an absolute measurement or an incrementalmeasurement.

[0032] According to the invention, the actuator device will in thepresence of certain conditions exert a force on at least one of theshifter elements in accordance with a predetermined characteristic,while during the actuation at least one characteristic electricalvariable of the control device and/or the actuator device is detectedand/or monitored as a function of time.

[0033] A characteristic electrical variable in the sense of the presentinvention is in particular a voltage or a current.

[0034] With preference, the characteristic electrical variable to detector monitor is the total amount of current consumed and/or generated bythe control device and/or the current consumed by the selector motorand/or the current consumed by the shifter motor and/or the currentconsumed by the actuating device. In particular, the process isvoltage-controlled, where voltage signals are given according to apredetermined characteristic, and the currents flowing as a result ofthe voltages are monitored or detected.

[0035] Instead of monitoring a current, it is also possible within thescope of the invention to monitor another characteristic electricalvariable. To represent the invention in simple terms, the example of avoltage controlled method is explained, in which a predetermined currentis monitored or detected. However, the invention also includes conceptswhere another first characteristic electrical variable is used insteadof a current, or another second characteristic electrical variable isused instead of a voltage.

[0036] According to the invention, the characteristic electricalvariable, meaning the current in the case of the representative example,is evaluated as a function of time according to a predeterminedevaluation characteristic in order to determine at least one of theshift positions of the transmission.

[0037] The predetermined shift positions that can be detected by one ofthe embodiments of the inventive method are in particular one or more ofthe shift-track end positions and/or the neutral position and/or anyposition where the first shifter element is located in the selectortrack.

[0038] The invention provides in particular that the evaluation of thecurrent as a function of time will indicate when the first shifterelement is positioned at a dead end, detents, specific locations withina track, or it will indicate in which track the shifter element iscurrently positioned.

[0039] The invention will be explained in further detail through theexample of a transmission with a shifter finger, where the latter isrepresentative of any kind of first shifter element.

[0040] In the present context, if a first shifter element or shifterfinger is said to run against a stop, dead end, or boundary, the latterterms are understood to mean either an actual physical barrier or theoccurrence of an effect that is comparable to a physical barrier. Aneffect comparable to an actual physical barrier means in particular thatanother element that is coupled to the movable element is running into astop or is otherwise constrained from continuing its movement. Aconstraint that prevents a continued movement can be realized inparticular by a preset limit in the control device or the actuatordevice. For example, an electric motor can be controlled so that it isswitched off when reaching a predetermined amount of displacement in agiven direction under a given set of conditions.

[0041] In the present context, if a movable element such as the firstelement or shifter finger is said to have reached an indent in a surfaceprofile, or a detent, this means that the element is engaged in anactual physical detent or an analogous position-defining feature, orthat another element that is coupled to the first element has a detentfeature that is in an engaged position.

[0042] The invention has the advantage that predetermined positions ofthe transmission can be safely recognized even in case of a failure ofthe position sensor device, so that incorrect gear shifts are avoided.For example, the invention provides the possibility of detecting endstops of the transmission, the release of a blocked synchronizer, adetent position for the neutral state, or bias-free, settled positionsof the transmission. The invention further provides the possibility thatthe position sensor device will adapt itself to these positions.

[0043] As a preferred concept, a method according to the invention canbe used as an emergency mode that is used under a predetermined set ofconditions. In particular, the emergency mode is started if the positionsensor device has been found to produce faulty information or if it hasfailed completely, or produces signals that are contradicted by otherfactors.

[0044] In accordance with a particularly preferred embodiment of theinvention, the electric current that is being monitored depends on theactivities of the selector motor and/or the shifter motor in accordancewith a predetermined characteristic. In particular, the electric currentis stronger at times when the selector- and/or shifter motor is running.When the selector- and/or shifter motor consumes an increasing amount ofpower, the monitored electric current will likewise show an increase.

[0045] The invention provides in particular, that starting and brakingcurrents are taken into account in the evaluation in accordance with apredetermined characteristic.

[0046] According to a particularly preferred embodiment of theinvention, the monitored electric current depends in a predeterminedcharacteristic manner on the travel path of the shifter finger and/or onthe force that is exerted on the shifter finger by the actuator device.

[0047] Preferred is a concept where the electric current represents acombined characteristic effect of the activities of the selector- and/orshifter motor, the travel path of the shifter finger and/or the forceacting on the shifter finger.

[0048] In particular, the invention provides that variable amounts ofresistance opposing a movement of the shifter finger will have aninfluence on the electric current. In particular, by monitoring thecurrent as a function of time, it is possible to determine whether theshifter finger is being pushed against an end stop and/or is positionedat an end stop and/or is running through a detent position and/or islocated at a detent position and/or whether a movement of the shifterfinger in a shift track has arrived at the selector track, or otherinformation about the movement and/or position of the shifter finger. Asa particularly preferred concept of the invention, detented positions ofthe shifter finger are associated with predetermined positions of thetransmission, particularly the neutral state and/or a bias-free positionin which a gear is engaged and/or at least one position within theselector track where a shift track branches off, or other characteristicpositions of the transmission.

[0049] According to a particularly preferred embodiment of theinvention, the current-monitoring function is performed on the totalcurrent of the control device and/or a current inside the shifter motorand/or the power current supplied to the shifter motor and or a currentinside the selector motor and/or the power current supplied to theselector motor.

[0050] A highly preferred embodiment of the inventive method providesthat the total current of the control device is monitored, but that thecontrol device supplies current only to the actuator device alone and/oronly to the shifter motor alone and/or only to the selector motor aloneduring the time period that is being monitored or evaluated.

[0051] Preferably, the current supplied to other consumer devices in thevehicle is measured in accordance with a predetermined characteristicand taken into account in the evaluation of the overall current balance.

[0052] As a preferred concept, the current as a function of time is usedunder certain conditions to detect when the shifter finger has reachedthe end point of a lateral constraint, for example when the shifterfinger moves out of a shift track into the selector track. To make thisdetection possible, the shifter motor and the selector motor are bothunder power during the movement in the shift track, but as long as theshifter finger is prevented from moving in the selector direction, theselector motor is stalled and its current flow is therefore increased.As soon as the shifter finger has reached the selector track and is thusfree to move in the selector direction, the current decreases. Thedecrease in the total current can serve as an indication that theshifter finger has reached the selector track.

[0053] According to a particularly preferred embodiment of theinvention, the shifter motor is switched off or, in more general terms,the actuation in the shift direction is terminated after detecting thatthe shifter finger has reached the selector track.

[0054] Also among the preferred concepts, the actuation in the shiftdirection may be continued for a predetermined time period or apredetermined distance after the shifter finger has reached the selectortrack.

[0055] With particular preference, the switch-off point in the shiftdirection is adapted to the geometry of the selecting/ shifting trackpattern as well as to the geometry of the shifter finger. With specialpreference, after reaching the selector track, the shifter finger isbrought into a position in which it can move in the selector track witha minimal amount of friction and/or without touching the lateralboundaries of the selector track.

[0056] According to a particularly preferred embodiment of theinvention, after detecting that the shifter finger has reached theselector track, it is moved to a predetermined position in the selectordirection. According to the invention, the predetermined position is aboundary of the selector track, in particular one of the end barrierslimiting the selector track in the lengthwise direction.

[0057] The move to an end barrier of the selector track can occurimmediately following the detection that the shifter finger has reachedthe selector track. Also among preferred concepts, the move to an endbarrier of the selector track is performed independently of whether ornot the arrival of the shifter finger at the selector track has beendetected. As a particularly preferred concept of the invention, the moveto the end barrier of the selector track serves to make an adjustment tothe position sensor device in the selector direction. This procedure maybe used, e.g., in a case where the position-sensor device for the shiftdirection is working correctly, but the detection in the selectordirection is incorrect or has failed.

[0058] In accordance with the invention, the current of the selectormotor or the total current of the actuator device is monitored while anactuator force is applied in the selector direction.

[0059] With preference, the selector motor is switched off after an endbarrier in the selector direction has been reached. Also as a preferredpossibility, the selector motor is reversed to run in the oppositedirection after reaching an end barrier of the selector track.

[0060] Under another preferred concept, the movement of the shifterfinger in at least one position is subjected to a local increase ordecrease in the opposing force in at least one of the tracks. Undercertain conditions, the local variation in the opposing force canmanifest itself by an increase or decrease in the actuator current, sothat the respective position can be detected by monitoring andevaluating the current.

[0061] A local variation in the opposing force can be effected inparticular by detents at intermediate positions between the end stops ofa track. More specifically, a component coupled to the shifter fingercan be equipped with a detent or can be moved into a detented position.

[0062] As a practical embodiment of the preceding concept, a secondshifter element, in particular a shifter shaft or shifting rod may havea surface profile with depressed and/or raised surface portions. Afeeler contact element biased by a spring force follows the profilecontour or exerts a force against the contour as the second shifterelement moves in relation to the contact feeler element. This creates avariable force opposing or assisting the movement of the second shifterelement, dependent on the location where the contact feeler element ispositioned on the profile, and also dependent on the direction ofmovement of the second shifter element. For example, a profiledepression is arranged in at least one fully engaged and bias-free gearposition and/or in the neutral position and/or at predeterminedpositions of the selector track where at least one shift track branchesoff.

[0063] Following is an example of how a detent arrangement affects theactuator current of a shifter shaft that performs gear shifts throughangular as well as axial movements. A single profile depression can beused to detect a position relative to both the shift direction and theselector direction. For example, the profile depression can be arrangedat a specific point on the shifter shaft so that the contact feelerelement engages the low point of the depression when the shifter fingeris at an intersection between the selector track and a shift track.

[0064] The foregoing example is used only to illustrate specialpossibilities of the invention without limiting the scope of theinvention in any way. A device where the resistance to the movement of ashifter element is used may also be configured in other ways.Furthermore the location of the movement-opposing or -assisting featurecan also be arranged at other essentially arbitrary locations of theselecting/shifting track arrangement. Also, a substantially arbitrarynumber of different movement-opposing or -assisting features can beemployed in an arrangement according to the invention.

[0065] As the shifter shaft is moved axially or rotated about itslongitudinal axis in the process of selecting and shifting, the contactfeeler element will in certain phases move towards a profile depression.

[0066] When the selector- or shifter motor is started up, an initialsurge in the motor current can be detected, manifesting itself as a peakin the time profile of the current. Subsequently, the current willsettle and stay at an essentially constant level until the contactfeeler element reaches the profile depression, unless there are otherfactors influencing the current. Examples of such other influencefactors include for example stall conditions where the shifter finger isacted on by a motor, but is constrained by a track boundary.

[0067] When the contact feeler element enters the profile depression, inthis case a bowl-shaped formation, the spring-biased contact feelerelement follows the down slope of the bowl. At first, the contact feelerelement moves closer to the central axis of the shifter shaft. Afterpassing through the bottom of the bowl, the contact feeler element(which stays in place while the shifter shaft moves) is pushed backagain against the spring force. The interactive force between thecontact feeler element and the profile surface is perpendicular to theprofile surface at the contact point. Thus, there is a force componentassisting the movement in a first phase where the contact feeler elementmoves towards the bottom of the bowl and opposing the movement in asecond phase where the contact feeler element moves away from the bottomof the bowl. Corresponding to the amount of the total force required tomaintain the movement, the motor current decreases in the first phaseand increases again in the second phase. Thus, a local dip followed by arise occurs in the profile of the actuator current. The low point of thecurrent can be used to detect when the contact feeler element is at thedetent or low point of the bowl-shaped depression. As the detentdepression corresponds to a certain position of the shifter fingerwithin the shifting/selecting track pattern, it is therefore possible todetect a position of the shifter finger based on the actuator current.

[0068] The foregoing concept can be used to detect for example when agear is settled into an engaged position, or when the transmission is inthe neutral position.

[0069] According to a particularly preferred embodiment of theinvention, the foregoing concept is used in a such a way that there is achange in the force that opposes the movement of the shifter finger inat least one place between the end stops of a track, and the currentprofile and/or the change in the opposing force is used to identifywhich track the shifter finger is moving in. As a preferred possibility,when the shifter finger is actuated in the shifting direction, thearrival at the selector track can be detected from the actuator current.Specifically, a depression in the surface profile would be arranged atthe intersection of a shifting track with the selector track. Therespective shifting track will preferably have additional profiledepressions, which can be detected from the variations in the actuatorcurrent as the shifter finger moves along the shifting track. Based onthe pattern of depressions detected, it will be possible to detect theposition of the selector track.

[0070] The foregoing concept of the invention is advantageous insofar asit allows the arrival at the selector track to be detected by actuatingthe shifter finger in the shifting direction only.

[0071] According to a particularly preferred embodiment of theinvention, different tracks, and especially different shifting tracks,can be identified or distinguished from each other by monitoring andevaluating the actuator current.

[0072] Under the invention, it is in particular envisaged that eachshifting track be distinguished by a characteristic number of profiledepressions and/or profile peaks or detents. As the shifter finger movesthrough the shifting track, the profile depressions manifest themselvesthrough local decreases followed by increases in the time profile of thecurrent. Based on the number of profile depressions detected in thismanner when moving through a shifting track, the respective shiftingtrack can be positively identified and distinguished from other shiftingtracks without the need for measuring signals of a displacement sensor.

[0073] The invention proposes the concept of detecting local ortransient changes in the force opposing the movement of the shifterfinger through the detection of local or transient extremes in thecurrent.

[0074] In particular, such extremes include maxima and minima.

[0075] In particular, an increase followed by a decrease in the opposingforce, as would occur at a profile peak, manifests itself as a local ortransient peak followed by a dip in the actuator current. A decreasefollowed by an increase in the opposing force, as would occur at aprofile depression, manifests itself as a local or transient dipfollowed by a peak of the actuator current.

[0076] In accordance with a particularly preferred embodiment of amethod according to the invention, certain gear positions are detectedaccording to a predetermined characteristic relationship, particularlyas part of an emergency procedure. Particularly preferred is a conceptwhere the transmission does not shift through all of the gears whenperforming the emergency procedure.

[0077] In particular, the invention proposes the concept for anemergency procedure to shift into gear positions in shift tracks thatare distinguished by an end stop, detent, or other movement-resistingfeature in the selector track at the point where the respective shifttrack branches off from the selector track.

[0078] A typical case in point is the double-H shift pattern, i.e., ashifting/selecting track arrangement with three selector track positionswhere shift tracks take off from the selector track, so that thetransmission can be shifted into a total of six different gears. Underan emergency procedure as described above, the transmission would moveinto the shifting tracks that branch off from the end point of theselector track. Typically, this means shifting into first, second, fifthand reverse gears. It is particularly preferred if the transmission alsofinds and positively identifies the neutral position during thisemergency procedure. In a particularly preferred embodiment for a shiftpattern where fifth and reverse gears branch off at essentially the sameselector position, the transmission will search for neutral, firstand/or second, and reverse gears.

[0079] A four-track pattern is defined as a shifting/selecting trackpattern where reverse, first, third and fifth gears lie in parallelshift tracks in the upper half of the pattern, and where second andfourth gears lie opposite first and third, respectively, in the lowerhalf of the pattern.

[0080] Preferably, a detent or resistance barrier is arranged in theselector track between the branch-off point for first/second and thebranch-off point for reverse gear. In the search procedure, the shifterfinger is moved towards this resistance barrier with a limited actuatorforce, so that the barrier, e.g., in the form of a profile peak, cannotbe overrun without increasing the actuator force. This resistancebarrier, which can also have the form of a profile depression, maylikewise be used to find and move into the first and second gearpositions under the emergency procedure.

[0081] As a preferred feature for an emergency procedure, after theshifter finger has reached an end of the selector track and is about tomove from there into a shift track, the shifter finger is subjected to acontinuing but preferably small force in the selector direction towardsthe end stop, to ensure that the shifter finger finds its way into theshift track.

[0082] In accordance with a particularly preferred embodiment of theinvention, when searching for a predetermined gear position and beforethe shifter finger has entered the respective shift track, anappropriate step is taken to confirm that the shifter finger is in thecorrect selector position from which the targeted shift track branchesoff. This confirmation can be achieved, e.g., by taking the direction oftravel into account in which the shifter finger was moving prior toreaching the branch point on the selector track.

[0083] For example, in a double-H shift pattern where the shifter fingerhas reached an end stop of the selector track while traveling with afirst sense of direction, it can be confirmed that the end stop for thattraveling direction belongs to the branch point for first/second gears.If the shifter finger has been moving in the opposite direction, it canbe confirmed that the end stop for that traveling direction belongs tothe branch point for reverse/fifth gears.

[0084] While the transmission searches for the different gear positions,the current is monitored, so that the end stops, detents, or otherbarrier features can be detected from the behavior of the current. Themovement of the shifter finger can be directed dependent on the behaviorof the actuator current, so that the shifter finger is moved in ashift-track direction when the correct position has been reached.

[0085] In accordance with a particularly preferred embodiment, theinventive concepts are used in a phase of gear engagement, particularlyunder an emergency procedure, to detect the point of synchronizationand/or the unlocking of the synchronization and/or the arrival at theend position of the shift track, and or the unbiased, engaged gearposition.

[0086] The point of synchronization in the present context means theposition at which the gears of a particular gear level are about toenter into meshing engagement. At this point, it will be necessary incertain situations for one of the gears to turn by a small amount inrelation to the other before the tooth profiles can mesh with eachother.

[0087] A completed synchronization or unlocked condition in the presentcontext means a state where the gears of the ratio level to be engagedare in a position where the tooth profiles can move into engagementwithout the lateral tooth flanks blocking each other, which wouldconstitute a kind of lock.

[0088] The invention proposes the concept of detecting one or more ofthe aforementioned positions or events on the basis of the actuatorcurrent.

[0089] For example, a point of synchronization can be detected by thefact that gears whose lateral flanks have come into mutual contact canunder certain conditions at least temporarily prevent the gears frommeshing with each other, so that further movement is blocked at leastuntil the blockage is released. This locked condition causes a momentaryincrease in actuator current. When the current returns to a lower level,this indicates that the blocked condition has ended.

[0090] When a renewed increase in actuator current is detected after apredetermined time interval, this can be used as an indication that theshifter finger has reached the end of the shifting track.

[0091] Preferably, the actuation of the first shifter element in theshifting direction for shifting into first gear is terminated when theend of the shifting track has been detected.

[0092] According to a particularly preferred embodiment of theinvention, the actuation in the shifting direction is continued for apredetermined time period after a resistance barrier has been detectedin the shifting track. This has the purpose of distinguishing temporarybarriers such as a blocked synchronizer process from permanent barrierssuch as the end of the shifting track. This distinction is particularlyimportant if at the time of putting the transmission in gear, the toothprofiles happen to be mutually positioned so that their lateral toothflanks are not interfering with each other, in which case no blockageoccurs.

[0093] According to a particularly preferred embodiment of theinvention, a shake-down phase is performed when the end stop of ashifting track has been detected in the course of shifting thetransmission into gear.

[0094] A shake-down phase in the present context means a pulsatingactuation of a movable element of the transmission. This can be achievedby driving the selector- and or shifter motor with voltage pulses ofalternating polarity for a predetermined amount of time. The alternatingpulses are for example in a range between 0.3 and 5 volts. Preferred arepulses between 0.3 and 3 volt, with special preference for pulsesbetween 0.5 and 2 volt.

[0095] The shake-down causes the shifter finger and/or a componentcoupled to the latter to settle into an unbiased (force-free)equilibrium position.

[0096] Subsequently, the actuation of the shifter finger is terminatedafter a predetermined time period has elapsed.

[0097] As a preferred concept of the invention, after the unbiasedposition has been found, a plausibility test is performed whether theactually engaged gear is the one that was intended. This can beestablished by checking whether the ratio between the engine rpm rateand a wheel rpm rate correlates correctly with the intended transmissionratio.

[0098] According to a particularly preferred embodiment, a shake-downphase is performed when the transmission is put into neutral, so thatthe shifter finger and/or transmission components coupled to the latterwill settle into an unbiased condition.

[0099] A process according to the inventive method is started withpreference after detecting certain kinds of faults of the sensor deviceand/or the actuator device and/or the control device. A fault in thepresent context means in particular any impairment of functionality. Afault in the present context can also mean a loss of confidence in theposition values determined by the position sensor device. The loss ofconfidence can occur, for example, if blockages of shift movements occurat unexpected times or in unexpected positions.

[0100] According to a particularly preferred embodiment of theinvention, a determination of a position through one of the proceduresof the inventive method may under certain conditions be performed as aredundant measure, for the purpose of adapting the position sensordevice or its output values to changes in the system.

[0101] According to a particularly preferred embodiment of theinvention, a redundant position information is used to control thetransmission only if the values generated by the position sensor devicehave positively been found to be faulty.

[0102] The invention provides a further operating method for a vehicletransmission in which predetermined shift positions, in particular atleast one position of full engagement of a gear and/or at least oneposition in the selector track, are associated with profile depressionsthat are arranged on a movable element. The method includes thefollowing steps:

[0103] a) Under predetermined conditions and in accordance with apredetermined characteristic, the transmission is actuated to seek aposition that is associated with a profile depression.

[0104] b) A shake-down or vibratory movement is carried out to settlethe first element (or another element coupled to the latter) into anessentially unbiased, force-free position, after detecting that thecontact feeler element has substantially arrived at the depression. Theshake-down movement is generated by applying an alternating pulsatingforce to at least one shifter element, so that the shifter element is atleast once pushed quickly back and forth.

[0105] The invention provides a further method of detecting a change inposition, or detecting a position relative to a reference point in atransmission. This further method includes the step of emulating atleast one actuator device by means of a model that is incorporated inthe control device. This method, too, applies to a transmission that hasdifferent rotary transfer ratios between an input- and output shaftcorresponding to the different shift positions. Shifting thetransmission into one of the positions requires a movement in the shiftdirection and in some cases also in the selector direction. The movementin the selector direction is controlled by a first electricallycontrolled actuator device, and the movement in the shift direction iscontrolled by a second electrically controlled actuator device. Thefirst and/or second actuator device is equipped with a displacementsensor device, and the transmission has at least one electric controldevice to control the actuator devices.

[0106] According to a proposed embodiment of the invention, the actuatordevice for the selector movement and/or shift movement is emulated inthe control device, e.g., through a model of a servo-control loop.

[0107] According to a preferred embodiment of the aforementioned method,the command signal by which a position-control unit directs themovements of an actuating device is used also as input for the servomodel that emulates the actuator device. As an example, the commandsignal can be an analog voltage signal.

[0108] The output signal delivered by the emulator model is preferablyan equivalent counterpart to the signal of the displacement sensordevice. The displacement sensor can be realized, e.g., by an incrementalposition sensor, in which case the output signal of the emulation modelis preferably made available in terms of angular increments or in radianunits.

[0109] It is particularly advantageous if the emulation model of anactuator device is based on characteristic variables or design dataand/or at least one measured quantity of the actuator device. If thelatter consists of a rotary drive mechanism, the characteristicvariables can consist in particular of an rpm rate and/or a rotaryacceleration, or of variables from which a rotary speed or accelerationcan be calculated. If an electric motor such as a DC motor is used as adrive source, the characteristic design data used in the emulator modelcan, e.g., consist of the moment of inertia of the rotor, the electricalresistance of the rotor, and/or a torque constant. For a measuredquantity, it is advantageous to use an rpm-dependent friction of themotor.

[0110] The use of an emulator model of the actuator device represents aparticularly advantageous means for detecting a failure and/ormalfunction of the displacement sensor. In practice, the faultrecognition is based on calculating and evaluating the differencebetween the respective output signals of the displacement sensor deviceand the emulator model. A fault is indicated if the difference exceeds agiven threshold. It is practical to set the sensitivity of the faultrecognition through an appropriate selection of the threshold value,preferably taking the accuracy of the emulator model and possibly otherfactors into account. In one advantageous embodiment, an on/offhysteresis is used for an indicator flag signaling a fault ormalfunction.

[0111] If a failure and/or malfunction has been recognized, appropriatemeasures are taken such as, e.g., initiating a special strategy foroperating faults and/or making an entry into a fault memory.

[0112] In regard to a special strategy for operating faults, referenceis hereby made to the German Patent Application Publication DE 199 00820, the content of which is expressly incorporated by reference in thepresent patent application.

[0113] According to a further concept of the invention, an adaptation ofthe model is advantageously performed at a time when the displacementsensor device is fully functional. In case there is a difference betweenthe output signals of the emulator model and the displacement sensor,the emulator model is adjusted to produce an output that more closelymatches the signal of the displacement sensor.

[0114] The invention provides a further embodiment of a method which isparticularly advantageous for controlling a transmission without thedisplacement sensor device that is part of the preceding embodiment. Inthis case, the displacement and/or position relative to a fixed point ofthe transmission is determined by the emulator model alone.

[0115] The scope of the invention also includes control devices that areequipped with a signal-evaluating capability and are operable to performany of the methods of the foregoing description. Specifically, suchcontrol devices electrically control an actuator device that applies anactuating force to a first and/or second shifter element of atransmission, where the first shifter element is movable in aselecting/shifting track arrangement and where the position of at leastone of the shifter elements can be detected by a position sensor.

[0116] Further included under the scope of the invention aretransmissions of the type described above with at least a first shifterelement that is movable in selecting/shifting track arrangement, and atleast one second shifter element, an electrically controlled actuatingdevice for at least one of the shifter elements, at least one controldevice for the actuator device, at least one position sensor device todetermine the shift position of the transmission at any given time and,in addition, a redundant sensor device performing in certainpredetermined situations a redundant determination of the shift positionrelative to the selector direction.

[0117] The invention further includes any transmission capable ofperforming one or more of the inventive methods described herein.

[0118] As a linguistic formality, where the names of features areconnected by the word “or”, this should be understood in the broadestsense, i.e., either as a logic type of “or” (one or the other or both)or an exclusive “or” (one or the other but not both), whichever fits thecontext.

[0119] The terms “control” and “regulation” and their derivatives areused herein with a broad range of meanings encompassing closed-loop aswell as open-loop control of devices, functions and processes, includingin particular the DIN (Deutsche Industrie-Norm) definitions forregulation and/or control).

[0120] The novel features that are considered as characteristic of theinvention are set forth in particular in the appended claims. Theinventive method itself, however, both as to its mode of operation andits application in a motor vehicle, together with additional featuresand advantages thereof, will be best understood upon perusal of thefollowing detailed description of certain presently preferred specificembodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0121] The embodiments of the invention as described and illustrated areintended to serve as examples only, and no limitations are therebyimplied. The description refers to the attached drawings, wherein

[0122]FIG. 1 represents a schematic view of a first vehicle in which theinventive method may be used;

[0123]FIG. 2 represents a schematic view of a second vehicle in whichthe inventive method may be used;

[0124]FIG. 3 represents a schematic view of a first shift pattern inwhich the inventive method may be used;

[0125]FIG. 4 represents the shift pattern of FIG. 3 correlated with asurface profile on a shifter shaft;

[0126]FIG. 5 represents a schematic view of a second shift pattern inwhich the inventive method may be used;

[0127]FIG. 6 represents a first example of a signal profile of acharacteristic electrical variable that can be used to detectpredetermined shift positions;

[0128]FIG. 7 represents a second example of a signal profile of acharacteristic electrical variable that can be used to detectpredetermined shift positions;

[0129]FIG. 8 represents a first example of a flow chart of a methodaccording to the invention;

[0130]FIG. 9 represents a second example of a flow chart of a methodaccording to the invention;

[0131]FIG. 10 represents time profiles of several differentcharacteristic variables which can be used according to the invention todetect predetermined shift positions;

[0132]FIG. 11 represents a third example of a flow chart of a methodaccording to the invention;

[0133]FIG. 12 represents a fourth example of a flow chart of a methodaccording to the invention;

[0134]FIG. 13 represents a schematic view of portions of a transmissionin which the method according to the invention can be used;

[0135]FIG. 14 represents a schematic view of a shift pattern correlatedwith a first signal profile.

[0136]FIG. 15 represents a schematic view of a shift pattern correlatedwith a second signal profile;

[0137]FIG. 16 represents an arrangement analogous to FIG. 13, with adifferent kind of redundant displacement sensor;

[0138]FIG. 17 represents an example of a block-diagram model of anactuator device; and

[0139]FIG. 18 represents an example of a flow chart of anerror-detection strategy.

DETAILED DESCRIPTION OF THE INVENTION

[0140]FIG. 1 gives a schematic view of a vehicle 1 with a drive unit 2such as a motor or combustion engine. The power train of the vehiclefurther contains a torque-transmitting device 3 and a transmission 4.The illustrated example shows the torque-transmitting device 3 arrangedin the torque flow path between the engine and the transmission, so thatthe driving torque generated by the engine is passed on by way of thetorque-transmitting device 3, the transmission 4, the drive shaft 5, andthe driving axle 6 to the wheels 6 a.

[0141] The torque-transmitting device 3 is configured as a clutch, suchas a friction clutch, laminar disc clutch, magnet powder clutch, orconverter bypass clutch. The clutch may be of the self-adjusting,wear-compensating type. The transmission 4 is shown as a manual shifttransmission in which the transmission ratio is changed in steps.However, under the concept of the invention, the transmission may alsobe an automated shift transmission in which the shifting process isautomated by means of at least one actuator. The term “automated shifttransmission” further means an automated transmission of a type wherethe tractive force is interrupted during gear shifts and where theshifting from one transmission ratio to another is performed by means ofat least one actuator.

[0142] It is also possible to use a conventional automatic transmissionof the type that works without interrupting traction during gear shiftsand is normally based on planetary gear stages.

[0143] As a further possibility, a transmission with a continuouslyvariable rotary transfer ratio, such as for example a cone-pulleytransmission, may be employed in embodiments of the invention. If aconventional automatic transmission is used, the latter may be equippedwith a torque-transmitting device 3, e.g., a clutch or friction clutch,arranged at the output side of the transmission. The torque-transmittingdevice can further be configured as a start-up clutch and/or as areverse-gear clutch and/or as a safety clutch in which the magnitude ofthe transmittable torque can be controlled at a targeted level. Thetorque-transmitting device can be a dry friction clutch, or a so-calledwet-running friction clutch that runs in a fluid, or it may consist of atorque converter.

[0144] The torque-transmitting device 3 has an input side 7 and anoutput side 8. A torque is transmitted from the input side 7 to theoutput side 8 through a contact force that is applied to the clutch disc3 a by means of the pressure plate 3 b, the diaphragm spring 3 c, therelease bearing 3 e, and the flywheel 3 d. The force is generated by anactuator pushing or pulling the release lever 20.

[0145] The torque-transmitting device 3 is controlled by means of acontrol unit 13 which may be configured as a control device with anelectronic module 13 a and an actuator 13 b. In another advantageousembodiment, the actuator and the electronic module may also beaccommodated in two separate subassembly units or housings.

[0146] The control unit 13 may contain the electronic circuits for thecontrol as well as for the power supply of the electric motor 12 of theactuator 13 b. This has the advantage that only one compact portion ofspace is needed for both the actuator and the electronics. The actuatorconsists of a motor 12, typically an electric motor driving a hydraulicmaster cylinder 11 through a gear mechanism such as a worm gearmechanism, a spur gear mechanism, a crank mechanism, or a threadedspindle mechanism. The master cylinder may be driven directly or by wayof a rod linkage.

[0147] The movement of the output element of the actuator, i.e., of thepiston 11 a of the master cylinder 11, is detected by a clutch travelsensor 14 which senses a position, or the speed or acceleration of achange in position, of an element whose displacement, speed oracceleration is in direct proportion to the displacement, speed oracceleration of the clutch. The master cylinder 11 is connected througha pressure conduit 9, normally a hydraulic line, to the slave cylinder10. The output element 10 a of the slave cylinder is coupled to therelease lever or release element 20. Thus, a movement of the outputelement 10 a of the slave cylinder 10 causes the release element 20 tobe moved or tilted to effect a controlled variation of the amount oftorque that is transmitted by the clutch 3.

[0148] The actuator 13 b that controls the torque-transmitting device 3may be based on a pressure-propagation principle, using a mastercylinder and slave cylinder communicating through a pressure medium. Thepressure medium can be a hydraulic fluid or a pneumatic medium. Themaster cylinder may be driven by an electric motor 12 that iselectronically controlled. However, instead of an electric motor, thedriving element of the actuator 13 b may also be based on another drivesource, e.g., driven by hydraulic pressure. It is also conceivable touse magnet-based actuators to set a position of an element.

[0149] The amount of torque transmitted through a friction clutch iscontrolled to a targeted level by applying pressure on the frictionlinings of the clutch disc between the flywheel 3 d and the pressureplate 3 b. The force that is exerted on the pressure plate and on thefriction linings is controlled by the position of the release element20, whereby the pressure plate is moved to or set and held at anyposition between two end positions. One end position represents a fullyengaged condition of the clutch, and the other end position represents afully disengaged condition. To set the transmittable torque at an amountthat is less than the current engine torque, the pressure plate 3 b ismoved to a position that lies in an intermediate range between the endpositions. By controlling the release element 20 to a set target, theclutch can be held at the targeted position. However, it is alsopossible to set the transmittable torque above the level of the currentengine torque. In this case, the torque generated by the engine ispassed on by the clutch, while torque fluctuations, especially abruptpeaks in the torque flow, are damped and/or isolated.

[0150] The control and regulation of the torque-transmitting devicefurther relies on sensors which at least part of the time monitor therelevant factors and provide the status data, signals and measurementvalues that are necessary for the control and are processed by thecontrol unit. The latter may also have communication lines to otherelectronic units such as, e.g., an electronic engine control unit, or anelectronic control of the anti-lock braking system (ABS), or ananti-slip regulation (ASR). The sensors detect, for example, rpm ratesof the vehicle wheels or of the engine, the position of the gas pedal,the position of the throttle valve, the currently engaged gear level ofthe transmission, driver-generated inputs that indicate an impendinggear change, and other characteristic information specific to thevehicle and the operating situation.

[0151]FIG. 1 shows a throttle valve sensor 15, an engine rpm sensor 16,as well as a vehicle speed sensor 17, which relay measurement data andinformation to the control device. The electronic unit, such as acomputer unit that is part of the control unit 13 a, is processing theincoming data and issues control commands to the actuator 13 b.

[0152] The transmission is configured as a step-shifting transmission,in which the transmission ratio is shifted in discrete, fixed steps bymeans of a shift lever. The shift lever may operate or actuate thetransmission directly. There is further at least one sensor 19 barranged at the shift lever 18 of the manual shift transmission, whichserves to detect when the driver intends to shift gears and/or whichgear is currently engaged, and to relay the information to the controldevice. The sensor 19 a is connected to the transmission and serves todetect the currently engaged gear of the transmission and/or to detect acondition that indicates that the driver is about to shift gears. Thedetection of the driver's intent to shift gears can be realized throughthe use of at least one of the sensors 19 a, 19 b, if the sensor is aforce sensor that responds to a force acting on the shift lever.Alternatively, the sensor could also be a position sensor ordisplacement sensor, in which case the control unit would recognize anintent to shift gears from a dynamic change of the position signal.

[0153] The control device is at least part of the time in signalcommunication with all of the sensors and evaluates the sensor signalsand input data which, in their totality, are referred to as the currentoperating point of the torque transfer system. Based on the operatingpoint, the control device issues control and regulation command signalsto the at least one actuator. The drive element 12 of the actuator, suchas an electric motor, operates under the command of the control unitthat controls the actuation of the clutch by means of a command signalthat depends on the measurement values and/or the system input dataand/or signals of the sensors. The control device has a control programin the form of hardware and/or software, which evaluates the incomingsignals and calculates or determines the output quantities based oncomparisons and/or functions and/or characteristic data arrays or curvefields.

[0154] The control unit 13 is advantageously equipped with units ormodules for the determination of torques, gear positions of thetransmission, amounts of slippage in the clutch, and/or differentoperating states of the vehicle, or there are signal connections fromthe control unit 13 to at least one of the aforementioned modules. Themodules or units may be implemented in the form of control programs inhardware and/or software. As a result, the incoming sensor signals allowa determination of the torque of the drive unit 2 of the vehicle 1, thegear position of the transmission 4, the amount of slippage in thetorque-transmitting device, as well as the current operating state ofthe vehicle. The gear-position determining unit detects which gear iscurrently engaged based on the signals from the sensors 19 a and 19 b.The sensors are coupled to the shift lever and/or to internal mechanicalelements of the transmission such as, e.g., a central shifting shaft orshifting rod, to detect the position or movement of these elements.There can further be a gas pedal sensor 31 arranged at the gas pedal 30to detect the position of the latter. A further sensor 32 may consist ofa binary on/off switch to indicate when the engine is idling, i.e., theswitch 32 is on when the gas pedal is not being depressed, and it is offwhen the gas pedal is being actuated. The gas pedal sensor 31, incontrast to the on/off switch 32, provides a quantitative signalrepresenting the degree of actuation of the gas pedal.

[0155] Further in FIG. 1, a brake-actuating element 40 is shown whichserves to apply the service brake or the parking brake. This can be abrake pedal, a hand-brake lever, or a hand- or foot-operated actuatingelement of the parking brake. At least one sensor 41 is arranged at theactuating element 40 to monitor the actuation of the latter. The sensor41 may be a digital sensor, e.g., a binary switch for detecting whetherthe actuating element is in an applied or non-applied state. This sensormay be connected to a signal device such as a brake indicator light toalert the driver that the brake is applied. This arrangement can be usedfor the service brake as well as for the parking brake. However, thesensor can also be configured as an analog sensor, e.g., as apotentiometer that measures the degree of displacement of the actuatingelement. This sensor, likewise, can be connected to an indicator signal.

[0156]FIG. 2 gives a schematic view of a power train of a motor vehiclewith a drive unit 100, a torque-transmitting device 102, a transmission103, a differential 104, drive axles 105, and wheels 106. Thetorque-transmitting device 102 is arranged at or connected to a flywheel102 a. The latter as a rule carries an external tooth profile 102 b thatserves to start the engine. The torque-transmitting device has apressure plate 102 d, a clutch cover 102 e, a diaphragm spring 102 f,and a clutch disc 102 c with friction linings. The clutch disc 102 c isinterposed between the pressure plate 102 d and the flywheel 102 a andmay be equipped with a damping device. An energy-storing device such asa diaphragm spring 102 f pushes the pressure plate axially towards theclutch disc. A clutch-actuating element 109 such as a hydraulicallyactuated concentric slave cylinder is used to actuate thetorque-transmitting device. A release bearing 110 is arranged betweenthe concentric slave cylinder and the prongs of the diaphragm spring 102f. As the release bearing is moved along the axial direction, it pushesagainst the diaphragm spring and thereby disengages the clutch. Theclutch may be configured either as a push-actuated clutch or apull-actuated clutch.

[0157] The actuator module 108 belongs to an automated shifttransmission and includes the actuator unit for the torque-transmittingdevice. The actuator module 108 operates internal shifter elements suchas, e.g., a shift-actuating cylinder or a rod mechanism, or a centralshifter shaft of the transmission. The actuation may work in a mannerwhere the gears can be engaged and disengaged in sequential order or inan arbitrary order. The clutch-actuating element 109 is operated by wayof the connection 111. The control unit 107 is connected to the actuatorthrough the signal line 112. The control unit 107 is further connectedby signal lines 113 to 115. The signal line 114 carries incomingsignals. The line 113 carries command signals issued by the controlunit. The connection 115, consisting for example of a data bus,exchanges signals with other electronic units.

[0158] To put the vehicle in motion or to accelerate the vehicle from astationary or slow rolling condition, the driver has to use only the gaspedal 30, as the controlled or regulated automatic clutch actuationcontrols the amount of transmittable torque of the torque-transmittingdevice. The degree of depression of the gas pedal is detected by the gaspedal sensor 31, and the control unit will accordingly implement a moreor less forceful or rapid start-up acceleration. The sensor signals fromthe gas pedal are used as inputs for the control of the start-up phaseof the vehicle.

[0159] In a start-up phase, the amount of transmittable torque is set asa control target by means of a given function or on the basis ofcharacteristic curves or curve fields that may be functions of theengine rpm rate. The latter may in turn be dependent on other quantitiessuch as the engine torque, that are correlated to the engine rpm ratethrough a characteristic relationship.

[0160] In a start-up process, essentially from a stationary orcrawl-speed condition, if the gas pedal is actuated by an amount a, theengine control device will direct the engine to generate an enginetorque of a certain magnitude. The control unit of the automated clutchactuation 13 controls the transmittable torque of thetorque-transmitting device in accordance with given functions orcharacteristic curve fields, so that a stationary equilibrium sets inbetween the engine torque and the clutch torque. The equilibrium ischaracterized dependent on the gas pedal displacement a by a specificstart-up rpm rate, a start-up torque generated by the engine, a specificamount of transmittable torque of the torque-transmitting device, and aspecific amount of traction torque delivered to the drive wheels. Thefunctional relationship between the start-up engine torque and thestart-up rpm rate will subsequently be referred to as the start-upcharacteristic. The gas pedal displacement a is proportionate to theaperture of the throttle valve of the engine.

[0161] Further in FIG. 2, a brake-actuating element 120 is shown whichserves to apply the service brake or the parking brake. This can be abrake pedal, a hand-brake lever, or a hand- or foot-operated actuatingelement of the parking brake. At least one sensor 121 is arranged at theactuating element 120 to monitor the actuation of the latter. The sensor121 may be a digital sensor, e.g., a binary switch for detecting whetherthe actuating element is in an applied or non-applied state. This sensormay be connected to a signal device such as a brake indicator light toalert the driver that the brake is applied. This arrangement can be usedfor the service brake as well as the parking brake. However, the sensorcan also be configured as an analog sensor, e.g., as a potentiometerthat measures the degree of displacement of the actuating element. Thissensor, likewise, can be connected to a signal indicator device.

[0162]FIG. 3 illustrates an example of a shift pattern 300 with aselector track and shift tracks, which is part of an arrangementaccording to the invention and also serves to give a clearer descriptionof a method according to the invention.

[0163] The selecting/shifting track pattern 300 in FIG. 3 has the shapeof a double-H. The shift tracks 302, 304, 306, 308, 310 belong to theforward gears one through five, respectively, and the shift track 312belongs to the reverse gear. The shift tracks are connected by theselector track 314.

[0164] The method according to the invention serves to detect when theshifter finger is positioned at predetermined end stops or predeterminedgear positions. The method can be used, e.g., as an emergency strategyduring a temporary failure of a displacement measuring device. It canalso be used to calibrate the displacement measuring device in aprocedure that is performed as a safety measure at predetermined timeintervals.

[0165] A method according to the invention will now be discussed inwhich the gear positions or the end positions of the respective shifttracks are determined in sequence for first, second, fifth and reversegear. The scope of preferred embodiments also includes other orders ofsequence.

[0166] The method is discussed for an exemplary case, where the shifterfinger (not shown in the drawing) is positioned at the outset in theselector track 314. The starting position of the shifter finger in theselector track 314 may have been detected by an inventive method that isnot described in detail within the context of FIG. 3.

[0167] The shifter finger (not shown) is pushed by a selector motoralong the double arrow 316 towards the end stop 318 of the selectortrack. During this activity, the current of the selector motor or thetotal current of a control device directing the selector motor ismonitored. For simplicity's sake, the following explanation willconsistently refer to the total current of the control device, althoughthe invention includes the possibility of detecting the currents of theshifter motor and selector motor separately.

[0168] During a start-up phase of the selector motor, the currentprofile of the control device will show a temporarily increased currentflow which is due to the start-up current of the selector motor. Afterthe starting phase, the current falls to a lower level and staysessentially constant until the shifter finger has reached the end stop318 of the selector track. After arriving at the end stop 318, theshifter finger continues to be pushed against the end stop by theselector motor, so that the stalled condition can be detected from astrong increase in the current. The position at the end stop 318 can bedistinguished from the end stop 320 based on the direction of movementof the shifter finger. The sense of direction can be determined, e.g.,by monitoring the signal of an incremental displacement sensor which isused to detect the motion of the shifter finger. As an alternative, aprofile indentation or a detent can be arranged at a short distance fromthe end stop 318 or at an appropriate place of the shifter shaft, whichwill manifest itself through a local variation of the current profilethat will occur at the end stop 318 but be absent at the end stop 320.

[0169] After the arrival of the shifter finger at the end stop 318 hasbeen detected, the selector motor is switched off, whereby a negativecurrent is induced which subsequently rises to the zero level. The endstop 318 can also be used as a reference for the calibration of thedisplacement measuring device in the selector direction. As analternative to switching off the selector motor, the latter could remainenergized to exert a very small force on the shifter finger in thedirection of the end stop 318 to ensure that the shifter finger is infact being moved along the shift track 302. For the movement in theshift track 302, the shifter motor pushes the shifter finger in thedirection towards the end stop 330 of the shift track 302. Initially,this will cause a start-up surge of the current which manifests itselfas a peak in the current profile. Subsequently, the current decreasesand then remains at a substantially constant level until the end stop330 has been reached. At the end stop 330 the current profile will atfirst show an increase as the shifter motor is stalled by the end stop330 opposing further movement of the shifter finger.

[0170] After the arrival at the end stop 330 has been recognized, theshifter motor is switched off, so that the inductive switch-off currentwill cause a dip into the negative of the current profile.

[0171] Following this, the shifter motor will push the shifter finger inthe opposite direction, and the arrival at the end stop 332 willmanifest itself by a current increase. The shifter motor is switched offat this point, which again causes an inductive switch-off current thatwill manifest itself through a negative transient in the currentprofile. Next, the shifter motor is energized to push the shifter fingerin the opposite direction, causing another start-up surge (transientpeak) in the current, whereupon the current level decreases to asubstantially constant level. After the selector track 314 has beenreached, the shifter motor is switched off and the selector motor isenergized to push the shifter finger in the direction towards theselector-track end stop 320. The arrival at the end stop 320 is againdetected from a strong rise in the current. In analogous manner, themovement is continued to the end stop 334 of the shift track 310 andsubsequently to the end stop 336 of the shift track 312. The positionsat the end stops 330, 332, 334, 336 are detected and used for thecalibration of the displacement sensor device.

[0172]FIG. 4 illustrates the same shifting/selecting track pattern 300with a schematic representation of a shifter shaft 350 which inaccordance with the movement of the shifter finger is moved axially inthe shifter direction symbolized by the double-headed arrow 352 orrotated about its axis in accordance with a movement of the shifterfinger in the selector direction.

[0173] A contour or detent profile 354 is provided on the shifter shaft350 with profile peaks 356, 358 and profile depressions 362, 364. At asubstantially fixed position, a spring-biased contact feeler element(symbolized by the arrow 366) pushes against the profile 354. The axialcomponent of the contact force variably opposes or assists the axialmovement of the shifter shaft 350 dependent on the position of thelatter. As a consequence, the actuator current profile, which is beingmonitored during the movement of the shifter shaft 350 or of the shifterfinger (not shown in FIG. 4), shows local extreme values when thecontact feeler element 366 is at one of the profile depressions 360,362, 364. An appropriate arrangement of a surface profile cooperatingwith a contact feeler element 366 can thus be used to detect by way ofthe actuator current profile when the shifter finger is located atpredetermined shift positions or in the selector track.

[0174]FIG. 5 illustrates an example of a selecting/shifting trackpattern 380 which may be part of a transmission in accordance with theinvention, or which can be used to perform a process according to theinvention.

[0175] The arrangement of FIG. 5 is also referred to as a four-trackpattern, where the four tracks belong to reverse, first/second,third/fourth, and fifth gear, respectively.

[0176] A reverse-gear barrier 382 is arranged between the shift track302/304 for first/second gear and the shift track 312 for reverse gear.In the current profile, the reverse-gear barrier 382 manifests itselflike an end stop when the shifter finger moves against it, so that theentry into reverse gear can be detected from the actuator current.

[0177]FIG. 6 illustrates an example of a profile graph of the current(in arbitrary units) of a shifter motor that can occur when the shifterfinger moves (as measured in position increments) through a shift trackthat is associated with a detent arrangement as shown in FIG. 4. Whenthe shifter motor is switched on, the current goes through a start-upsurge that manifests itself as a peak in the area 390 of the graph,which is followed by a sharp descent in the area 392. In this phase, theshifter finger is positioned substantially in the surface profiledepression 364 (FIG. 4). The continued movement where the contact feelerelement 366 glides over the profile peak 358 can be detected from thelocal maximum 394 of the current in FIG. 6. This is followed by a markeddecline of the current towards a local minimum value at 396, whichcorresponds to the depression 362 in the surface profile 354 of FIG. 4.The position of the contact feeler element 66 in the depression 362corresponds essentially to a position of the shifter finger in theselector track 314 of the shift pattern of FIG. 4. As the contact feelerelement glides over the surface profile peak 356, the current rises toanother local maximum at 398 and subsequently falls to a local minimum400 as the contact feeler element glides into the surface profiledepression 360. When the shifter finger has reached the end of the shifttrack, the stalled condition of the shifter motor can be detected fromthe strong rise in the current in the area 402 of the graph.

[0178] The graph of FIG. 7 represents the total current of a controldevice that can occur when the shifter finger travels along the selectortrack. When the selector motor starts up, a current surge can bedetected in the area 410 of the graph. During the movement along theselector track, the current remains essentially constant within ±1measuring unit, as seen in the portion 412 of the graph. At the end stopof the selector track, a strong current increase of the current can bedetected as shown in the area 414 of the graph.

[0179]FIG. 8 represents an example in flow-chart format, where themethod according to the invention is used as an emergency procedure tomove the transmission into predetermined positions within theselecting/shifting track pattern and to detect the predeterminedpositions. The same procedure can also be used to adjust or calibrate adisplacement sensor device.

[0180] The procedure is started at step 420. In step 422 a shake-downphase is initiated to ensure that the shifter finger or a movableelement connected to the latter is settled into an unbiased, force-freecondition.

[0181] In step 424, the shifter finger is moved back and forth in theselector direction. In step 426, a test is performed whether end stopswere detected in step 424. This test is made by measuring the totalcurrent of the control device. If no stops were detected in step 426,the process is terminated in step 428. In the affirmative case of step426, i.e., if end stops were detected, a further test is made in step430, whether the time interval from detecting one stop to the other wasshorter than a predetermined amount of time. As the process is directedthrough the voltage transmitted by the control device, the fact that thetime interval between opposite end stops was shorter than apredetermined value can be used as an indicator that the shifter fingeris positioned in a shift track. In the negative case of step 430, i.e.,if the time interval between end stops is found to be longer than apredetermined amount of time, this can serve as an indicator that theshifter finger is positioned in the selector track. The method proceedsto step 446, which will be described below after step 444.

[0182] In the affirmative case of step 430, i.e., if the time intervalis shorter than a predetermined amount, the method continues in step432, where the shifter finger is moved back and forth in the shiftdirection. In step 434, a test is performed as to whether or not endstops were detected in the back-and-forth movement of step 432. As instep 426, this test is based on measuring the total current of thecontrol device. In the affirmative case of step 434, i.e., if end stopswere detected, a test is made in step 438, whether the selector trackhas been found. The detection of the selector track can be based, e.g.,on a detent at the intersection of the selector track and the shifttrack which produces a characteristic response in the total currentsignal of the control device when the shifter finger reaches theselector track.

[0183] In the negative case of step 438, i.e., if the selector track wasnot detected, a further test is made in step 440 whether the number oftimes that the method failed to detect the selector track exceeds agiven threshold number. In the affirmative case, the process isterminated in step 442. In the negative case, the method loops back tostep 432.

[0184] If step 438 indicates that the shifter finger has reached theselector track (i.e., the contact feeler element has reached thecorresponding detent position of the surface profile), a vibratory orshake-down phase is initiated in step 444 to ensure a settled, bias-freeposition in the selector track. Subsequently, in step 446, the shifterfinger is moved in the selector track direction towards the shift trackof first/second gear. As mentioned above, step 446 is also performedafter a negative outcome of step 430.

[0185] Next, a test is made in step 448 by measuring the total currentof the control device, whether or not a stop was detected in theselector track. In the negative case, the method loops back to step 424.In the affirmative case, a shake-down process is performed in step 450to settle the shifter finger in a defined position in the selector trackbetween first and second gear.

[0186] Step 452 collectively represents the continuation of the methodin which the shifter finger is moved under voltage control into thepositions of first and second gear as well as fifth and reverse gear,while monitoring the current during the movement.

[0187]FIG. 9 illustrates another application of the inventive method totake a gear out of engagement and to detect when the selector track hasbeen reached.

[0188] In step 460, the shifter finger is actuated by forces in theshift direction as well as the selector direction. The force in theshift direction is oriented towards the selector track. The totalcurrent of the control device is monitored over time. In step 462, thetotal current is found to be decreasing. This serves as an indicatorthat the shifter finger, which was previously constrained by the shiftertrack, has left the latter and has become free to move in the selectortrack.

[0189] In step 464, the shifter motor is switched off, after a smallvoltage pulse may have been applied in the shift direction (optional).

[0190]FIG. 10 represents time graphs of different characteristicvariables during a time phase when the inventive method is beingperformed. In particular, FIG. 10 serves to explain how the inventionproposes to detect positions of the shifter finger based on the timeprofiles of certain characteristic electrical variables.

[0191] The three graphs of FIG. 10 represent the voltages 470 and 472 ofthe selector motor and the shifter motor, respectively, the totalcurrent 474 delivered by the control device, and the displacementcomponents 476 and 477 of a movable element in the shift and selectordirections, respectively. The movable element is in particular a shifterfinger.

[0192] In the left-hand portions of the time graphs 470, 472, 474, 476,477, as indicated by the broken line 480 and the arrow 478 pointingtowards the left, a profile graph is illustrated from which a positionin the selector track can be recognized.

[0193] The continuation of the time graphs 470, 472, 474, 476, 477 tothe right of the broken line 480 will serve to explain through anexample how positions and states of the shifter finger can be detectedon the basis of the time profiles of the illustrated variables.

[0194] The method is performed under voltage control. This means that asubstantially constant voltage is used to energize the shifter andselector motor, so that the voltage signals 470, 472 have constantvalues. It should be noted at this point, that the scope of theinvention nevertheless also includes a control that works with variablevoltages.

[0195] The start of the shifter and selector motors causes a currentsurge in the control device at the point 482. At this point in time, theshifter finger is constrained in a shift track, so that it can only movein the shift direction as can be seen in the area 484 of thedisplacement graph.

[0196] After the start-up phase of the motors, the current in thecontrol device decreases and continues at an essentially constant levelduring the phase 486. As the shifter finger is constrained by the shifttrack from moving transverse to the latter, it can only advance in theshift direction, as indicated by the increasing displacement in thebottom graph of FIG. 10. At the position 488 in the displacement graph,the shifter finger has essentially reached the selector track. Due tothe actuation force of the selector motor, the shifter finger from thispoint on can also move in the selector direction, as indicated by theportion 490 of the displacement graph.

[0197] As the shifter finger is no longer constrained by the shift trackand begins to move in the selector direction, the total current of thecontrol device decreases and settles at an essentially constant level inthe area 492.

[0198] By detecting the foregoing development in the current profile, itis possible to determine that the movable element has reached theselector track.

[0199] The continuation of the graphs in FIG. 10 to the right of thebroken line 480 represents two cases (a) and (b) which can occuralternatively. If at the time 494, the shifter finger runs into a stopin the selector direction while the selector motor continues to receivea voltage as shown by the graph 472, the total current increases asshown at 496 and then settles at a higher, essentially constant level498. The shifter finger continues to move in the shift direction, asshown in the portion 500 of the displacement graph. If at the time 502,the shifter finger runs into a stop in the shift direction, the currentincreases again in the area 504 and then settles again at a higher,essentially constant level 506.

[0200] If the shifter finger at the time 494 is blocked both in theshift and selector direction, the total current of the control devicewill rise to a higher level in the area 508, essentially equal to thecurrent level 506. Thus, a higher current level that reflects blockagein both directions can be detected already between the times 494 and 502and interpreted as a position where the movable element is constrainedfrom further movement by stops in both directions.

[0201]FIG. 11 shows as an example in flow-chart format how limitationsin the lengthwise direction of the selector track can be detected.

[0202] In step 520, the selector motor is energized with current, sothat the shifter finger moves in the lengthwise direction of theselector track.

[0203] In step 522, a rise in the total current of the control device isdetected, indicating that the shifter finger has reached a stop at theend to the selector track.

[0204] In step 524, the selector motor is switched off.

[0205]FIG. 12 shows as an example in flow-chart format how the inventivemethod can be used under an emergency procedure to put the transmissioninto predetermined gears, such as first, second and reverse gear.

[0206] In step 530, a voltage is applied to the shifter motor to movethe shifter finger along a shift track.

[0207] In step 532, a rise in the current of the control device isdetected, which is followed by the detection of a decrease in current instep 534. This indicates that the shifter finger has run into a kind oftemporary barrier in the shift direction. This happens when asynchronization point is reached, which temporarily blocks the shiftingmovement and causes the current to rise. After the rpm rates aresynchronized, the blockage is released so that the shifter finger cancontinue its movement in the shift direction, which causes the currentto decrease again.

[0208] In step 536, the current is found to increase again and to remainat the increased level for at least a predetermined length of time. Thiscan be interpreted as an indication that the shifter finger has reachedthe dead end of the shift track. The shifter motor is switched off atthis point. Subsequently, voltage pulses of alternating polarity areapplied to the shifter motor in order to cause the shift mechanism tosettle in a bias-free position.

[0209] In step 538, the shifter motor is switched off, after apredetermined time period has elapsed, for example 200 to 1000milliseconds. Delaying the switch-off point by a predetermined amountserves to ensure that the shifter finger is not at a synchronizationpoint.

[0210]FIG. 13 represents a schematic view of portions of a transmissionaccording to the invention.

[0211] The components of the transmission that are shown include inparticular a control device 550, a selector motor 552, a shifter shaft554, a shifter finger 556, and a shifting rod 558. A shifter motor isnot shown in this example.

[0212] An incremental sensor device for the displacement in the selectordirection is arranged at the selector motor (not shown).

[0213] An additional incremental displacement sensor 560 is arranged asa redundant means of detecting displacement in the selector direction.

[0214] The redundant incremental displacement sensor 560 as well as theselector motor 552 have signal connections to the control device 550, assymbolized by the lines 562 and 564.

[0215] The redundant incremental displacement sensor 560 uses anon-contacting principle to sense a surface profile of the shifter shaft554 as the latter moves along the sensor. The sensor 560 is based, e.g.,on the Hall-effect sensor principle or an inductive sensor principle.

[0216] Each of the FIGS. 14 and 15 shows a selecting/shifting trackarrangement.

[0217] The graphs 570 and 572 below the representations of theselecting/shifting track arrangements represent sensor signals of thekind that could be produced by the redundant incremental displacementsensor of FIG. 13. As shown in FIG. 14, the sensor or switch 560 couldgive a signal when the shifter finger has reached one of the positionswhere the shift tracks branch off from the selector track.

[0218] Alternatively, the sensor 560 could also be designed to give asignal only when the shifter finger is at one specific position withinthe selector track, e.g., the middle shift track in a double-Harrangement.

[0219] With preference, the redundant incremental displacement sensor560 for the selector direction has a coarser measuring resolution thanthe primary incremental sensor device that is arranged, e.g., at theselector motor.

[0220] The arrangement of FIG. 16 differs from FIG. 13 essentially inthe redundant incremental displacement sensor which in the case of FIG.16 is configured as a mechanical, spring-biased contact feeler elementthat follows a contour profile of the shifter shaft 554.

[0221] The block diagram 1700 of FIG. 17 represents a schematic model ofan actuator device. A target value is generated in the electric controldevice 1701 of the transmission and sent to a position regulator 1702which, as a result, generates a corresponding voltage U_(A). The voltageU_(A) is transmitted by way of an output stage 1703 and serves tocontrol an actuator device such as a rotary electric motor 1704. Theactuator device 1704 moves the actual shifter elements of thetransmission 1705 by way of a motion-transfer mechanism (not shown). Inthe case of a shift transmission that works in discrete steps throughdifferent gear pairs, the shifter elements are the sliding sleeves thatengage and disengage the free gears. An incremental displacement sensor1706 generates a signal indicating the position or a change in theposition of a movable element in relation to a reference point. Inanother embodiment, it may also be advantageous to use other kinds ofdisplacement sensors including, e.g., absolute displacement sensors suchas potentiometers. The signal generated by the displacement sensor 1706is fed back to blocks 1701 and 1702 and at the same time transmitted toan error-detection unit 1707. The voltage U_(A)generated in block 1702is further entered into an emulator unit 1708, i.e., a computer model ofan actuator device that is implemented in an electrical control device.

[0222] The portion of FIG. 17 that is framed by a broken lineillustrates the details of the block 1708, i.e., an emulation of a drivesource for an actuator, in this case a rotary electric DC motor. Themodel uses an appropriate transfer function to generate a signal that isequivalent to the displacement signal generated by the incrementaldisplacement sensor 1706 as a result of a voltage signal U_(A) comingout of block 1702. The transfer function of the emulator model 1708 isbased on the following set of equations:

U _(A) =R _(A) ·I _(A) +C _(M)·ω_(M)  (1)

M _(A) =C _(M) ·I _(A)  (2)

J _(M)·{dot over (ω)}_(M) =M _(A) −d·ω _(M)  (3)

[0223] $\begin{matrix}{ \Rightarrow{\overset{.}{\omega}}_{M}  = {{\frac{c_{M}}{R_{A} \cdot J_{M}} \cdot U_{A}} - {( {\frac{c_{M}^{2}}{R_{A} \cdot J_{M}} + \frac{d}{J_{M}}} ) \cdot \omega_{M}}}} & (4)\end{matrix}$

[0224] The symbols used in the foregoing equations will be defined inthe next-following paragraph below. The transfer function correspondingto equations (1) to (4) describes a servo-loop of a type known as IT₁(integrating control loop with a time lag). To represent the entirecontrol loop consisting of the control device and the actuator device, atransfer behavior known as PT₂ (proportional control with a second-ordertime lag) will be entirely adequate. An alternative embodiment isconceivable where the emulator model would be used alone without theincremental position sensor to determine a change in position an/or theposition itself in relation to a reference point. In this latter case,it is advantageous to use a more advanced model of the actuator drivemechanism.

[0225] The emulator model 1708 in FIG. 17 is represented in detail bythe functional blocks 1709 to 1716. In block 1709, the input quantityU_(A) is multiplied by the reciprocal value 1/R_(A) of the rotorresistance R_(A) of the actuator motor. After block 1710, the feedbackfrom block 1714 is subtracted. Block 1710 performs a division by themoment of inertia J_(M) of the rotor of the actuator motor. After block1710, the feedback from block 1713 is subtracted. In block 1712, anintegration is performed to calculate the angular velocity ω_(M) of theactuator motor. In block 1714, the result of block 1712 is multiplied bythe velocity-dependent friction constant d of the actuator drive and fedback to the output of block 1709. In block 1713, the result of block1712 is multiplied by the quotient C_(M)/R_(A) and fed back to theoutput of block 1710. A further integration of the angular velocityω_(M) in block 1715 produces the angular position φ_(M). In block 1716,the angular position φ_(M) (e.g. in radian units) is converted to aquantity that corresponds to the increments measured by the incrementalposition sensor.

[0226]FIG. 18 shows an example of an error-detection strategy inblock-diagram format. Block 1801 of the block diagram 1800 stands for aposition controller generating a control signal and sending itsimultaneously along two different paths. From the left-hand output ofblock 1801, the control signal is fed through an end stage (block 1802)to a drive motor (block 1803) causing a position change which, in turn,is detected by a displacement sensor (block 1804) such as an incrementalposition sensor. From the right-hand output of block 1801, the samecontrol signal is sent to an emulator model of the drive motor (block1805) which computes a signal that is the theoretical counterpart of theactually detected signal of block 1804. In block 1806, the differencebetween the actual and the theoretical signal is determined. Block 1807performs a comparison whether or not the difference is larger than agiven threshold value. In the affirmative case of block 1807, an entryis made into an error memory (block 1808), and an error-managingstrategy is initiated in block 1809. In the negative case of block 1807,the displacement-sensor signal is accepted as correct. In block 1810,the emulator model (block 1805) is adjusted so that the computed signalsvalues of the emulator model (block 1805) will more closely match theactual signal values of the displacement sensor (1804).

[0227] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic and specific aspects of theaforedescribed contribution to the art and, therefore, such adaptationsshould and are intended to be comprehended within the meaning and rangeof equivalence of the appended claims.

What is claimed is:
 1. A method of detecting a change in positionrelative to a reference point of a transmission that is shiftable into aplurality of shift positions corresponding to different rotary transferratios between an input shaft and an output shaft, wherein changes fromone shift position to another are associated with movements of a firstshifter element in a two-dimensional shift pattern comprising a selectortrack and shift tracks, a first electrical actuator actuates movementsalong the selector track, and a second electrical actuator actuatesmovements along the shift tracks, at least one of the actuatorscomprises a displacement-sensor device, and the transmission comprisesan electrical control device to control the actuators; the methodcomprising the step of emulating at least one of the actuators by meansof a model in the electrical control device.
 2. The method of claim 1,wherein the actuator emulation is performed by means of a control-loopemulator.
 3. The method of claim 2, wherein the at least one actuatorand the control-loop emulator are given equivalent input signals.
 4. Themethod of claim 3, wherein a voltage is used as input signal for thecontrol-loop emulator.
 5. The method of claim 4, wherein the voltagecomprises the input voltage of a position controller.
 6. The method ofclaim 2, wherein the control-loop emulator generates an emulator outputsignal that is equivalent to a displacement-sensor output signal.
 7. Themethod of claim 6, wherein the emulator output signal comprises one ofan angular position and a quantity from which an angular position can becalculated.
 8. The method of claim 7, wherein the emulator output signalcorresponds to a magnitude of an angle expressed as a number ofincrements.
 9. The method of claim 7, wherein the emulator output signalcorresponds to a magnitude of an angle expressed in radian units. 10.The method of claim 2, wherein the control-loop emulator usescharacteristic variables of the actuator device that is being emulated.11. The method of claim 10, wherein the characteristic variablescomprise at least one of an rpm rate and a rotary acceleration of theactuator device that is being emulated.
 12. The method of claim 2,wherein the control-loop emulator uses characteristic design parametersof the actuator device that is being emulated.
 13. The method of claim12, wherein actuator device comprises an electric motor with a rotor anda stator and the characteristic design parameters comprise at least oneof a moment of inertia, an electrical resistance, and a torque constantof the rotor.
 14. The method of claim 2, wherein the control-loopemulator uses at least one measured quantity of the actuator device thatis being emulated.
 15. The method of claim 14, wherein the measuredquantity consists of a speed-dependent amount of friction.
 16. Themethod of claim 1, wherein the model serves to detect a malfunction ofthe displacement-sensor device.
 17. The method of claim 16, wherein themodel produces an emulator output signal, the at least one actuatorproduces an actuator output signal, and the malfunction is detected byfinding a difference between said output signals.
 18. The method ofclaim 17, wherein an error-managing strategy is initiated afterdetecting the malfunction.
 19. The method of claim 6, wherein theemulator output signal is used as a substitute for thedisplacement-sensor output signal to control the actuator that is beingemulated.
 20. The method of claim 18, wherein in addition an entry ismade into an error memory.
 21. The method of claim 1, wherein at a timewhen the displacement sensor device is fully functional, if adiscrepancy is detected between the emulator output signal and thedisplacement-sensor output signal, an adjustment is made to reduce saiddiscrepancy.
 22. The method of claim 21, wherein said adjustmentconsists of adapting the model so that the emulator output signal willmore closely match the displacement-sensor output signal.
 23. A methodof detecting a change in position relative to a reference point of atransmission that is shiftable into a plurality of shift positionscorresponding to different rotary transfer ratios between an input shaftand an output shaft, wherein changes from one shift position to anotherare associated with movements of a first shifter element in atwo-dimensional shift pattern comprising a selector track and shifttracks, a first electrical actuator performs movements along theselector track, and a second electrical actuator performs movementsalong the shift tracks, and the transmission comprises an electricalcontrol device to control the actuators; the method comprising the stepof emulating at least one of the actuators by means of a model in theelectrical control device.
 24. A control device for a vehicletransmission, said transmission comprising: a shift pattern with aselector track and shift tracks; a first shifter element, movable in theshift pattern; a second shifter element; at least one electricallycontrolled actuator device for actuating at least one of said shifterelements; a position-sensor device for detecting a current position ofat least one of said shifter elements; wherein the control devicecomprises an emulator model of the at least one actuator device.
 25. Acontrol device for a vehicle transmission, said transmission comprising:a shift pattern with a selector track and shift tracks; a first shifterelement, movable in the shift pattern; a second shifter element; atleast one electrically controlled actuator device for actuating at leastone of said shifter elements; wherein the control device comprises anemulator model of the at least one actuator device.
 26. A vehicletransmission that has a plurality of different operating statescorresponding to different rotary transfer ratios between an input shaftand an output shaft, said transmission comprising a shift pattern with aselector track extending in a selector-track direction and shift tracksextending in a shift-track direction; a first shifter element, movablein the shift pattern; a second shifter element; an electricallycontrolled actuator device for actuating at least one of said shifterelements; an electric control device for controlling the actuatordevice; a movable element indicative of said shift position and aposition-sensor device for detecting a current position of said movableelement; and at least one redundant sensor device operable underpredetermined conditions to perform redundant determination of saidshift position relative to the selector-track direction.
 27. The vehicletransmission of claim 26, wherein the second shifter element comprises adetent profile and the redundant sensor device comprises a feeler deviceoperable to follow the detent profile when the second shifter elementmoves in the selector-track.
 28. The vehicle transmission of claim 27,wherein the feeler device operates according to a contact-freeprinciple.